Internal combustion engines have a cylinder head and a cylinder block, which are connected to one another at the assembly faces thereof to form the individual cylinders, i.e. combustion chambers. The cylinder head is often used to accommodate the valve gear. The purpose of the valve gear is to open and close the intake and exhaust ports of the combustion chamber at the right times.
To accommodate the pistons and the cylinder liners, the cylinder block has a corresponding number of cylinder bores. The piston of each cylinder of an internal combustion engine is guided in a cylinder liner in a manner which allows axial movement and, together with the cylinder liner and the cylinder head, the piston delimits the combustion chamber of a cylinder. In this arrangement, the piston head forms part of the inner wall of the combustion chamber and, together with the piston rings, seals off the combustion chamber with respect to the cylinder block and the crankcase, thus preventing any combustion gases or any combustion air from entering the crankcase and preventing any oil from entering the combustion chamber.
The piston serves to transmit the gas forces generated by combustion to the crankshaft. For this purpose, the piston is connected in an articulated manner, by means of a gudgeon pin, to a connecting rod, which, in turn, is mounted movably on the crankshaft. The crankshaft, which is mounted in the crankcase, absorbs the connecting rod forces resulting from the gas forces due to fuel combustion in the combustion chamber and the inertia forces due to the non-uniform movement of the components of the power plant. The oscillating stroke motion of the pistons is transformed into a rotating rotary motion of the crankshaft. In this motion, the crankshaft transmits the torque to the drive train. Some of the energy transmitted to the crankshaft is used to drive auxiliary units, such as the oil pump and the generator, or serves to drive the camshaft and hence to actuate the valve gear.
In general and in the context of the present disclosure, the upper crankcase half is formed by the cylinder block. The crankcase is completed by the lower crankcase half, which can be mounted on the upper crankcase half and serves as an oil sump. The upper crankcase half has a flange surface to receive the oil sump, i.e. the lower crankcase half. In general, a seal is provided in or on the flange surface in order to seal off the oil sump or crankcase with respect to the surroundings. The connection is often made by means of a bolted joint.
To receive and support the crankshaft, at least two bearings are provided in the crankcase, generally being embodied in two parts and each comprising a bearing saddle and a bearing cover that can be connected to the bearing saddle. The crankshaft is supported in the region of the crankshaft journals, which are arranged, spaced apart along the crankshaft axis and are generally designed as thickened shaft offsets. The bearing covers and the bearing saddles can be designed as separate components or can be formed integrally with the crankcase, i.e. the crankcase halves. Bearing shells can be arranged as intermediate elements between the crankshaft and the bearings.
In the assembled state, each bearing saddle is connected to the corresponding bearing cover. One bearing saddle and one bearing cover in each case—if appropriate in conjunction with bearing shells as intermediate elements—form a bore for receiving a crankshaft journal.
The bores are generally supplied with engine oil, i.e. lubricating oil, and therefore, ideally, there is a load bearing lubricating film formed between the inner surface of each bore and the associated crankshaft journal as the crankshaft rotates, as in a plain bearing. As an alternative, it is also possible for a bearing to be of one-piece design, e.g. in the case of a built-up crankshaft.
To supply the bearings with oil, a pump for delivering engine oil to the at least two bearings is provided, and, via an oil circuit, the pump supplies engine oil to a main oil gallery, from which passages lead to the at least two bearings. To form the main oil gallery, a main supply passage is often provided in the cylinder block and is aligned along the longitudinal axis of the crankshaft.
According to previous systems, the pump is supplied with engine oil stemming from an oil sump via an intake line, which leads from the oil sump to the pump, and may ensure a sufficiently large delivery flow, i.e. a sufficiently large delivery volume, and may ensure a sufficiently high oil pressure in the supply system, i.e. in the oil circuit, in particular in the main oil gallery.
Another possible consuming unit in the abovementioned sense which requires an oil supply is the camshaft holder, for example. The explanations given already in respect of the support of the camshaft apply analogously. The camshaft holder is also generally supplied with lubricating oil, for which purpose a supply passage has to be provided.
Other possible consuming units are, for example, the bearings of a connecting rod or of a balancer shaft, where provided. An oil spray cooling system is likewise a consuming unit in the abovementioned sense, wetting the piston head with engine oil from below, i.e. from the crankcase side, by means of nozzles for the purpose of cooling and thus requiring oil, i.e. requiring a supply of oil. A hydraulically actuated camshaft adjuster or other valve gear components, e.g. those for hydraulic valve lash compensation, likewise have a requirement for engine oil and require an oil supply. An oil filter, or oil cooler provided in the supply line is not a consuming unit in the aforementioned sense. Admittedly, these components of the oil circuit are also supplied with engine oil. By its very nature, however, an oil circuit entails the use of these components, which have only tasks, i.e. functions, which relate to the oil as such. It is only a consuming unit which renders the oil circuit necessary.
The friction in the consuming units to be supplied with oil, e.g. the bearings of the crankshaft or between the piston and the cylinder liner, depends on the viscosity and hence the temperature of the oil provided and contributes to the fuel consumption of the internal combustion engine. Fundamentally, the aim is to minimize fuel consumption. In addition to improved, e.g. more effective, combustion, reducing the friction power is among the foremost aims. Moreover, reduced fuel consumption also contributes to a reduction in pollutant emissions.
With respect to reducing the friction power, rapid warming of the engine oil and rapid heating of the internal combustion engine are helpful, especially after a cold start. Rapid warming up of the engine oil during the warm-up phase of the internal combustion engine ensures that there is a correspondingly rapid decrease in viscosity and hence a reduction in friction or friction power. Previous systems include concepts in which the oil is warmed up actively by means of an external heating device. However, the heating device is an additional consuming unit in respect of fuel use, and this runs counter to the aim of reducing fuel consumption.
Other concepts envisage storing the engine oil warmed up during operation in an insulated container and using it when required, e.g. when restarting the internal combustion engine. The disadvantage with this procedure is that the oil warmed up during operation cannot be kept indefinitely at a high temperature, for which reason it is generally useful to warm up the oil again during the operation of the internal combustion engine.
Both an external heating device and an insulated container lead to an additional installation space requirement in the engine compartment and are detrimental to maximum-density packaging of the drive unit.
Reducing the friction power by rapid warming up of the engine oil is also made more difficult by the fact that the cylinder block or cylinder head are thermally highly stressed components which require effective cooling and are therefore often fitted with coolant jackets to form a liquid cooling system. The thermal economy of a liquid cooled internal combustion engine is governed primarily by this cooling system. The cooling system is designed with a view to protection from overheating and not with a view to warming up the engine oil as quickly as possible after a cold start.
Fitting the internal combustion engine with a liquid cooling system requires the arrangement of coolant passages which carry the coolant through the cylinder head and/or the cylinder block, i.e. at least one coolant jacket. The coolant, in general water containing additives, is delivered by means of a pump arranged in the cooling circuit, with the result that it circulates in the coolant jacket. In this way, the heat released to the coolant is dissipated from the interior of the cylinder block or cylinder head and, in general, is removed from the coolant again in a heat exchanger.
Compared with other coolants, water has the advantage that it is non-toxic, easily available and inexpensive and furthermore has a very high heat capacity, for which reason water is suitable for removing and carrying away very large quantities of heat, and this is generally seen as an advantage. On the other hand, the corrosion associated with water of the components supplied with coolant, and the comparatively low maximum permissible coolant temperature of about 95° C., which is a co-determinant of the temperature difference between the coolant and the components to be cooled and hence of the heat transfer, are disadvantageous.
If the intention is to remove less heat from the internal combustion engine, in particular the cylinder block, the use of other cooling fluids, e.g. oil, may be expedient. Oil has a lower heat capacity than water and can be heated up further, i.e. to higher temperatures, thereby making it possible to reduce the cooling capacity. The problem of corrosion is eliminated. Oil can be allowed to come into contact with components, especially moving components, without putting at risk the ability to function of the internal combustion engine.
An oil-cooled internal combustion engine is described by German Laid-Open Application DE 199 40 144 A1, for example. Moreover, the use of oil as a coolant for the cooling circuit has further advantages, in particular the advantage that an oil cooling system and the associated coolant jackets can be formed together with the oil supply system of the internal combustion engine, i.e. a common, coherent oil circuit is formed. After a cold start, the oil is warmed up more quickly owing to the fact that it flows through the at least one coolant jacket, thereby making it possible to shorten the warm-up phase.
However, the inventors herein have recognized an issue with the above approach. Routing oil through the cylinder block coolant jacket delays the warm-up of the cylinder block following an engine cold start, reducing the temperature of the exhaust produced in the engine and delaying light-off of downstream aftertreatment devices.
Accordingly, a method for warming up an internal combustion engine with at least one cylinder, a cylinder block which is formed by an upper crankcase half mounted to a lower crankcase half, said lower crankcase half containing an oil sump which is fed, via a supply line, by a coolant jacket, an inlet side of said coolant jacket supplied in turn with oil via the oil sump by an oil pump is provided. In one example, the method comprises releasing oil from the coolant jacket via gravity to reduce a cooling capacity of the internal combustion engine.
In this way, the cylinder block can be rapidly heated. This method of warming the block does not require additional heating units or insulated oil storage, although such additional units or stage may be used, if desired. Increasing the speed at which the cylinder block is heated is advantageous for operating conditions of the engine as well as for the use of accessories within the vehicle including cabin heat.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.